Mimeo DH-64
April 17, 1957
Purdue University
Agricultural Experiment Station
Lafayette, Indiana
THE MAKING AND PRESERVATION OF SILAGE
By
D. L. Hill, Dairy Department;
R. C. Pickett, Agronomy Department; and F. L. Patterson, Agronomy Department
Silage is the product of the controlled natural fermentation of green material.
The preservation of feed in this way is not a new process since it is known that green crops were placed in silos centuries ago. Good silage is a valuable feed in that it need not differ greatly in composition from that of the original crop. Even here there are losses, but it offers a means by which many crops can be most efficiently stored and fed. The development of field choppers and power equipment for handling the green crop has greatly increased the willingness of farmers to make silage.
The advantages of harvesting and storing the crop as silage, compared to other methods, are as follows:
1.	Silage saves feed.
a. Permits better use of crops not well adapted to curing, as hay.
b. Permits saving the crop regardless of the weather since it prevents losses due to leaching by rain and the mechanical losses of hay-making,
2.	It permits harvesting grasses and legumes at the most favorable stage of maturity.
3.	It may be more easily fed than hay.
The primary disadvantage of silage is that the per acre cost of harvesting and storing meadow crops as silage is generally greater than for making hay. It is possible that the additional feed saved and the increase in quality could off-set the increased cost.
The Ensiling Process
The secret of good silage making lies in controlling the fermentation. It is absolutely necessary that the fermentation take place in the absence of air. When a crop is placed in the silo, the temperature rises until all the entrapped air is exhausted. Ordinarily, temperatures should not rise above 100°F. Temperatures higher than this indicate the presence of too much air. Coarse chopping and not enough packing favor the development of high temperatures. If air continues to penetrate the mass, then molds eventually develop.
Shepherd and co—workers of the USDA have described the changes that take place in the silo as follows:

"Enzymes are also active during this time. They break down sugars into alcohol, carbonic acid, water, and acetic, lactic and butryric acids. The enzymes act on proteins to some extent, forming amino acids, peptides and some ammonia."

"As plant respiration and the activity of plant enzymes slow down, the activity bacteria, yeasts, and molds increases. Molds cease growing as soon as the air is exhausted, yeasts soon disappear, and only the bacteria remain active thereafter. Bacteria produce additional acid from soluble carbohydrates and from alcohol, and are